This application claims the priority of Korean Patent Application No. 2003-38518, filed on Jun. 14, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
An apparatus and method consistent with the present invention relates to operating an image display device, and more particularly, to an apparatus and a method for controlling a convergence of a projection television in which video patterns used for controlling the convergence can be generated so as to allow the projection television to have an overall uniform luminance level, and luminance levels of the video patterns in random positions of the projection television can be freely controlled.
2. Description of the Related Art
A projection television includes R (red), G (green), and B (blue) cathode ray tubes (CRTs) which display R, G, and B color images to project the R, G, and B color images on a screen, respectively.
The R and B CRTs are biased toward both sides of the G CRT, respectively. Thus, biased R, G, and B color images are projected on the screen of the projection television. A convergence control operation is performed so that the R, G, and B CRTs output equal color luminance levels so as to improve the resolution of the screen.
FIG. 1 is a view for explaining a process of controlling a convergence of a conventional projection television. A screen 100-1 on which a video is displayed is installed on a front surface of a projection television 100. As shown in FIG. 2, video patterns used for the convergence are displayed on the screen 100-1. Although not shown in FIG. 2, the projection television 100 includes an image projector which emits R, G, and B beams, a reflective mirror which reflects the R, G, and B beams toward the screen 100-1, and a remote control receiver which receives convergence control signals. A controller 104 drives a transfer unit 101 to transfer the projection television 100 to an imaging position of a charge-coupled device (CCD) camera 102. A remote control transmitter 103 transmits signals for displaying the video patterns to the screen 100-1 of the projection television 100 in order to control the convergence. The CCD camera 102 images the video pattern displayed on the screen 100-1 of the projection television 100. The controller 104 determines, using predetermined reference video patterns, whether the convergence of the screen 100-1 of the projection television 100 is currently within an allowable error. If the convergence is not within the allowable error, the controller 104 compensates for an error in the convergence using an additional controlling device.
U.S. Pat. No. 5,614,792 discloses such a method of controlling a convergence.
As described above, in a projection television, R and B CRTs are biased toward both sides of a G CRT. Due to this structural problem, a reddish image is formed in the left portion of a screen and a bluish image is formed in the right portion of the screen during the control of the convergence of the projection television. Also, the luminance of a marginal portion of the screen is poorer than the luminance of a central portion of the screen.
Accordingly, during the process described with reference to FIG. 1, luminance levels of R, G, and B video patterns may be different on the marginal and central portions of the screen. As a result, an image classification rate of the CCD camera 102 may deteriorate.